Cryoablation, a therapy that uses that removal of heat from tissue, is often used to treat cardiac conditions such as cardiac arrhythmias. In most cryoablation procedures, a pressurized refrigerant is circulated within the tip of a cryoablation catheter, where the refrigerant expands and absorbs heat from surrounding tissue. As the tissue freezes, blood adjacent the treatment site may also freeze, creating an “ice ball” that temporarily adheres the treatment element (for example, a cryoballoon or thermally conductive area at the tip of the cryoablation device) to the tissue at the treatment site, a phenomenon called cryoadhesion.
Cryoadhesion is advantageous in that it helps prevent the cryoablation device from moving away from the target treatment site of a beating heart. However, research has shown that a freeze-thaw-freeze cycle more effectively ablates tissue than a single longer freeze-only cycle. Although more efficient lesion creation is desired, the freeze-thaw-freeze cycle may also result in the thawing of the ice ball that keeps the cryoablation device in place. As a result, the device must be repositioned, which may be complicated and time-consuming. Further, some cryoablation procedures, such pulmonary vein isolation (PVI), involve the use of fluoroscopy to visualize the position of the device and to make sure that, for example, the pulmonary vein is completely occluded. Fluoroscopy involves x-ray visualization; consequently, each time the ice ball thaws and the cryoablation device is repositioned, the patient and the user are exposed to an increased amount of radiation.
Therefore, it is desirable to provide a method and system for more efficient cryoablation, while reducing the need for fluoroscopy.